Linear Hall Device Based Field Oriented Control Motor Drive System

ABSTRACT

A motor control system for a permanent magnet synchronous motor (PMSM) uses two linear Hall devices to produce a first signal indicative of a strength of a first magnetic field component produced by a set of rotor magnets and to simultaneously produce a second signal indicative of a strength of second magnetic field component produced by the rotor magnets that is approximately orthogonal to the first magnetic field component. An angular position and angular velocity of the rotor is calculated based on the first signal and the second signal. A plurality of phase signals is produced based on the calculated angular position and angular velocity. Current in a plurality of field windings of the motor is controlled using the plurality of phase signals.

CROSS REFERENCE TO RELATED APPLICATION(S)

This continuation application claims priority to U.S. patent applicationSer. No. 14/960,164, filed Dec. 4, 2015, which application is herebyincorporated herein by reference.

FIELD OF THE INVENTION

This disclosure relates motor drive systems, and in particular to motordrive system that uses perpendicularly arranged linear Hall devices.

BACKGROUND OF THE INVENTION

Brushless DC (direct current) electric motor (BLDC motors, BL motors)also known as electronically commutated motors (ECMs, EC motors) aresynchronous motors that are powered by a DC electric source via anintegrated inverter/switching power supply, which produces an AC(alternating current) electric signal to drive the motor. In thiscontext, AC does not imply only a sinusoidal waveform, but rather abi-directional current with no restriction on waveform. Additionalsensors and electronics may control the inverter output amplitude andwaveform in order to control DC bus usage/efficiency and frequency (i.e.rotor speed).

Digital motor control was first introduced to overcome the challengesthat traditional analog systems had in handling drift, aging ofcomponents and variations caused by temperature. Flexible softwarealgorithms not only eliminated tolerance issues relating to components,they enabled developers to dynamically accommodate variations inenvironmental conditions over time. For example, rather than only beingable to turn a fan motor full on or off, fan speed can now be adjustedbased on system temperature with a digital implementation. Additionally,systems may calibrate themselves, thus eliminating the need to scheduleregular, manual maintenance.

Hall sensors are the industry choice for medium sensitivity magneticsensors due to low cost, small area, and easy integrability. However,semiconductor Hall sensors may suffer from offset resulting fromnonidealities such as mismatch, doping variations, and undesiredpiezoelectric effects. A technique referred to as “spinning current” maybe used to reduce the offset.

The so called “Hall Effect” occurs when a magnetic field is orientedperpendicular to an electric current. The magnetic field generates avoltage difference across a conductor, called the Hall Voltage, in adirection which is perpendicular to both the direction of the magneticfield and the direction of the current flow. By measuring the Hallvoltage it is possible to determine the magnitude of the magnetic field.Typical Hall sensors usually include a strip or plate of an electricallyconductive material with an electric current flowing through the plate.When the plate is positioned in a magnetic field such that a componentof the field is perpendicular to the plate, a Hall voltage is generatedwithin the plate in a direction that is perpendicular to both thedirection of the magnetic field and the direction of the current flow.

Semiconductor Hall effect sensors produced using current techniquestypically include a sensing element produced from silicon. The magneticsensitivity of these devices is directly related to the electronmobility, mu, of the material used to construct the sensing element.Silicon typically has an electron mobility of approximately 1500cm²/(Vs).

BRIEF DESCRIPTION OF THE DRAWINGS

Particular embodiments in accordance with the invention will now bedescribed, by way of example only, and with reference to theaccompanying drawings:

FIGS. 1A-1B are illustrations of an exemplary permanent magnetsynchronous motor (PMSM);

FIGS. 2-4 illustrate the operation of a conventional horizontal Halleffect device;

FIGS. 5A, 5B, and 6 illustrate the operation of a vertical Hall effectdevice;

FIGS. 7A-7D illustrate the results of processing signals provided by avertical and a horizontal Hall device in an exemplary PMSM;

FIG. 8 is a block diagram of a complete motor control system usingperpendicular linear Hall sensors;

FIG. 9 is an illustration of placement of 2D linear Hall sensors in anexemplary PMSM;

FIG. 10 is a schematic illustrating an electrical equivalent of a Halldevice;

FIG. 11 is a flow diagram illustrating operation of linear Hall devicebased field oriented control motor drive system; and

FIG. 12 illustrates a process for calculating speed and angle using anon-linear observer.

Other features of the present embodiments will be apparent from theaccompanying drawings and from the detailed description that follows.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Specific embodiments of the invention will now be described in detailwith reference to the accompanying figures. Like elements in the variousfigures are denoted by like reference numerals for consistency. In thefollowing detailed description of embodiments of the invention, numerousspecific details are set forth in order to provide a more thoroughunderstanding of the invention. However, it will be apparent to one ofordinary skill in the art that the invention may be practiced withoutthese specific details. In other instances, well-known features have notbeen described in detail to avoid unnecessarily complicating thedescription.

The permanent magnet synchronous motor (PMSM) can be thought of as across between an AC induction motor (ACIM) and a brushless DC motor(BLDC). They have rotor structures similar to BLDC motors which containpermanent magnets. However, their stator structure resembles that of itsACIM cousin, where the windings are constructed in such a way as toproduce a sinusoidal flux density in the air gap of the machine. PMSMmotors have the same winding structure as a BLDC motor but with asinusoidal back EMF waveform, achieved by shaping the permanent magnetsin the rotor structure.

However, unlike their ACIM relatives, PMSM motors perform poorly withopen-loop scalar V/Hz control, since there is no rotor coil to providemechanical damping in transient conditions. Field Oriented Control (FOC)is the most popular control technique used with PMSMs. As a result,torque ripple can be extremely low, on par with that of ACIMs. However,PMSM motors provide higher power density for their size compared toACIMs. This benefit is because with an induction machine, part of thestator current is required to “induce” rotor current in order to producerotor flux. These additional currents generate heat within the motor.However, the rotor flux is already established in a PMSM by thepermanent magnets on the rotor.

Field-oriented motor drive systems have several well-known benefits,such as: maximize motor torque per amp; improved and simplified motordynamics; and provide smoother torque production than trapezoidaldrives. They fall into two categories: sensored and sensorless.“Sensorless” drive systems employ current and voltage measurements alongwith knowledge of motor parameters and a dynamic model to estimate therotor electrical angle. “Sensored” drive systems rely on angular sensorssuch as optical encoders or resolvers to directly measure the shaftangle.

Sensorless FOC drive systems provide a compact solution; however, theymay have startup and low speed issues. Initial position detection may benecessary because it is hard to distinguish between north and southpoles. Therefore, significant processing may be required.

Sensored FOC drive systems have a high startup reliability and providegood torque production at low speed. Better velocity control at lowspeeds relative to the rated speed is possible. However, an angularsensor is required. In the past, angular sensors have been delicate andexpensive. For example, an optical encoder may cost more than $50. Asensored FOC system with an angular encoder may require more space thana sensorless system and require more wires and components.

The general concept of digital motor control is well known; see e.g.“Designing High-Performance and Power-Efficient Motor Control Systems”,Brett Novak et al., June 2009, which is incorporated by referenceherein.

The general concept of integrated motor controllers is well known; see,e.g. “Increased integration, improved feature sets and new software formotor control systems: C2000™ Piccolo™ F2805x microcontrollers”, PatrickCarner, November 2012, which is incorporated by reference herein.

Embodiments of the present disclosure may provide an integrated sensoredFOC system in which space and cost are minimized, as will be describedin more detail below.

FIG. 1A is an illustration of an exemplary permanent magnet synchronousmotor (PMSM) 100. In this example, a rotor 120 is configured to rotate ashaft 124 within a stator 110. Stator 110 includes a set of coils, asindicated at 111. Rotor 120 includes a set of permanent magnets, such assouth (S) polarity magnet 121 and north (N) polarity magnet 122.

Most PMSMs utilize permanent magnets, such as magnets 121, 122, that aremounted on the surface of the rotor. This configuration makes the motorappear magnetically “round”, and the motor torque is the result of thereactive force between the magnets on the rotor and the electromagnetsof the stator formed by coils 111. This configuration results in theoptimum torque angle being 90 degrees, which may be obtained byregulating the d-axis current to zero in a typical FOC application.

FIG. 1B illustrates an exemplary magnetic field that may be produced bythe rotor magnets 121, 122 of rotor 120. The tangential field will bestrongest between the magnets, as illustrated at 135, and weakest at thecenter of each magnet. The radial field will be the strongest at thecenter of each magnet, as illustrated at 134, and weakest between themagnets. An axial field component (not shown) may extend parallel to theaxis of rotation of the rotor.

Basically, there are two kinds of Hall effect sensors. One type is a“linear” device, which means the output of voltage linearly depends onmagnetic flux density. The other type is referred to as a “threshold”device, or a “digital” device, which means there will be a sharpdecrease of output voltage at a threshold magnetic flux density. LinearHall sensors are utilized herein to produce signals that areproportional to the pending magnetic flux.

Linear Hall devices 131, 132 may be co-located adjacent to each other tosense the radial and tangential magnetic fields produced by thepermanent magnets on rotor 120. In some embodiments, Hall devices 131,132 may each be packaged in a separate module. In this case, they shouldbe located close to each other so that they are sensing the tangentialand radial field strength in roughly the same location in order tosimplify signal interpretation. They should also be placed perpendicularto each other in order to accurately sense the tangential and radialmagnetic flux. This configuration of two perpendicularly positioned Halldevices is referred to as “two dimensional” (2D) herein.

In some embodiments, both Hall devices may be fabricated on a sameintegrated circuit die. In this manner, they will be located closetogether on the same die. A horizontal Hall device and a vertical Halldevice may be formed in order to create a perpendicular relationshipbetween the two Hall devices.

In another embodiment, the two Hall devices may be configured so thatone Hall device is sensitive to radial magnetic flux while the otherHall device is sensitive to axial magnetic flux, i.e. flux that isapproximately parallel to the axis of rotor 120.

FIG. 2 is an illustration of an exemplary horizontal Hall sensor (HS)device 200. FIG. 3 is an isometric view of HS 200. The general conceptof Hall sensor is well known and need not be described in detail herein.As mentioned above, the “Hall Effect” occurs when a magnetic field isoriented perpendicular to an electric current. The magnetic fieldgenerates a voltage difference across a conductor, called the HallVoltage, in a direction which is perpendicular to both the direction ofthe magnetic field and the direction of the current flow. By measuringthe Hall voltage, it is possible to determine the magnitude of themagnetic field.

In this example, Hall sensor element 202 may be fabricated on asubstrate 220 using known or later developed fabrication techniques. Thekey factor determining sensitivity of Hall Effect sensors is highelectron mobility. The following materials are especially suitable forHall Effect sensors: gallium arsenide (GaAs), indium arsenide, (InAs)indium phosphide (InP), indium antimonide (InSb), graphene, etc.

Contact regions 204, 206 are formed in contact with element layer 202 inorder to provide a bias current 210 through the Hall element layer andto sense a resulting Hall Effect voltage 212.

Hall element 202 may be patterned into a traditional cross shape, asillustrated in FIG. 2. In other embodiments, other element shapes may bepatterned, such as an octagon or substantially octagonal, a triangle orsubstantially triangular, a quatrefoil or substantially quatrefoilshaped, a circle or substantially circular shape, etc. Similarly,depending on the geometry of element layer 202, the number of contactpads 204, 206 and corresponding wires may be altered to fit a givenapplication.

In this example, Hall voltage 212 may be represented by expression (1).

$\begin{matrix}{V_{Hall} = \frac{I_{bias}B_{Z}}{nte}} & (1)\end{matrix}$

where:

-   -   I_(bias)=the current across the shape    -   B_(z)=the magnetic field normal to the shape    -   n=is the charge carrier density    -   t=thickness of the Hall element    -   e=the elementary charge

This design results in a sensitivity of approximately 300 V/AT(volts/amp*Tesla). For example, a Hall voltage of approximately 30 uVwill be produced with a bias current of 100 uA in a 1 mT field. Thechannel resistance may be approximately 5.7 k ohms.

FIG. 3 illustrates a magnet 230 positioned above Hall element 202 in atypical sensing configuration. Flux lines 232 from magnet 230 thatpenetrate Hall element 202 in a perpendicular or somewhat perpendicularmanner with respect to the flow of bias current 210 produce a Halleffect voltage 212 that is formed across contacts 206.

FIG. 4 is an illustration of horizontal Hall device 200 that is packagedin a typical surface mount package mounted on a substrate 440. Substrate440 may be a rigid or flexible printed circuit board, for example. Thesubstrate may be any commonly used or later developed material used forelectronic systems and packages, such as: silicon, ceramic, Plexiglas,fiberglass, plastic, metal, etc., for example. Hall device 200 isreferred to as a “horizontal” device because the Hall element isposition parallel to substrate 440; this orientation makes it sensitiveto magnetic flux 232 from a magnet 230 that is moving in a directionperpendicular 434 to substrate 440.

FIG. 5A, 5B are cross sectional views of an exemplary vertical Halldevice 500 that is formed in a p-type semiconductor substrate 520. Adeep nwell (dnwell) 522 may be formed in substrate 520 using knowndiffusion techniques. A shallow pwell (spwell) 524 may be formed arounddnwell 522 for isolation using known diffusion techniques. Contacts 504,505, 506 may be formed by diffusion in dnwell 522. Bias current 510 maybe injected into dnwell 522 via contact 504 and return bias current 511may be collected via contacts 505. A Hall voltage 512 may be formedacross contacts 506 in response to a magnetic field applied to dnwell522.

FIG. 5B illustrates how bias current 510 flows through dnwell 522.Vertical Hall device 500 is most sensitive to magnetic flux 532 that isperpendicular to dnwell 522 and therefore in the plane of substrate 520.

FIG. 6 is an illustration of vertical Hall device 500 that is packagedin a typical surface mount package mounted on a substrate 640. Substrate640 may be a rigid or flexible printed circuit board, for example. Thesubstrate may be any commonly used or later developed material used forelectronic systems and packages, such as: silicon, ceramic, Plexiglas,fiberglass, plastic, metal, etc., for example. Hall device 500 isreferred to as a “vertical” device because the Hall element 522 isperpendicular to substrate 640. It is sensitive to magnetic flux 632from a magnet 630 that is moving in a direction parallel 634 tosubstrate 640.

FIGS. 7A-7D illustrate the results of processing signals provided by avertical Hall device, such as vertical Hall device 500, and a horizontalHall device, such as horizontal Hall device 200, in an exemplary PMSM,such as PMSM 100. In general, vertical Hall devices have a lowersensitivity than horizontal Hall devices. They also have a higherresidual offset as compared to a horizontal Hall device.

Referring to FIG. 7A, plot line 750 illustrates raw low pass filteredsensor data from a linear horizontal Hall device that is aligned to besensitive to radial magnetic flux produced by the rotor magnets 121, 122of rotor 120, referring back to FIG. 1A. Similarly, plot line 751illustrates raw filtered sensor data from a linear vertical Hall devicethat is aligned to be sensitive to tangential magnetic flux produced bythe rotor magnets 121, 122 of rotor 120. In both cases, the plot linesrepresent magnetic flux strength in milliTeslas (mT) vs. time as rotor120 rotates through several electrical cycles. In this example, twohorizontal Hall sensors, which are oriented 90° with respect to oneanother, are used. Both sensors have the same sensitivity (V/mT). Thegraphs indicate that the tangential magnetic field is weaker.

In another example in which a 2D Hall sensor is used, it would beappropriate to align it such that the vertical Hall sensor picks up theradial field and the horizontal Hall sensor picks up the tangentialfield, since a horizontal Hall sensor is typically more sensitive than averidical Hall sensor.

FIG. 7B illustrates the result of applying a gain to the radial magneticplot 750 and a gain to the tangential magnetic plot 751 to make theamplitude of the gain-adjusted radial plot 752 equal to the amplitude ofthe gain-adjusted tangential plot 753.

FIG. 7C illustrates the result of computing angular position (Phase) vs.time for a given rotation speed of rotor 120 using the gain adjustedHall sensor data, as shown by plot line 754. Similarly, plot line 755illustrates the result of computing angular position of rotor 120 usingdata obtained from an optical encoder. The angular position may becomputed from the sensor data using known or later developed algorithms.For example, the angle may be determined based on the two field strengthsignals by either calculating a four quadrant arc tangent directly orusing a non-linear observer to compute the angle indirectly. Computationof an electrical angle directly using four quad arctan is illustrated byexpression (2).

θ_(e)=arctan (Hr, Ht)   (2)

where:

-   -   Hr is the radial field strength    -   Ht is the tangential field strength

FIG. 12 illustrates a process for calculating speed and angle using anon-linear observer. The four quad arctan method is more sensitive tonoise measurement and harmonics in the sensed radial and tangentialmagnetic signals. The non-linear observer process includes an integratorthat acts as a filter. In this example, the radial field strength signal1201 is scaled by the output of cosine function 1211 while thetangential field strength signal 1202 is scaled by the output of sinfunction 1210 and then combined in summer 1205. Function 1206 sums thescaled input, where the input has been multiplied by a proportional gainKp, and the scaled integral of the input, where the input has beenintegrated and multiplied by a integrational gain Ki. Function 1208integrates the input to translate from angular speed to angularposition.

Referring again to FIG. 7C, notice that there is essentially nodifference between the low cost Hall sensor results and the expensiveoptical sensor results.

FIG. 7D illustrates phase error over time. In a FOC control system,torque “loss” is proportional to 1-cos(θ_err), where θ_err is theangular measurement error. Assuming the DC error can be corrected (it'sdue to mechanical misalignment), the error is equivalent to a torqueloss of less than 1 percent.

FIG. 8 is a block diagram of a complete motor control system 800 usingtwo linear Hall sensors 801, 802. A PMSM that has a stator 810 withfield windings and a rotor 820 that has a plurality of permanent magnetsmay be controlled by motor control system 800.

As described above in more detail, one linear Hall device 801 may beplaced adjacent rotor 820 in order to detect the radial magnetic fieldproduced by the rotor magnets of rotor 820. Similarly, a second linearHall device 802 may be placed adjacent rotor 820 and in proximity toHall device 801 in order to detect the axial or tangential magneticfield produced by the rotor magnets of rotor 820. As described above inmore detail, these two linear Hall sensors are co-located perpendicularto each other in order to sense two orthogonal components of themagnetic field produced by the rotor magnets of rotor 820 as it rotates,or while it is stationary.

Analog front ends (AFE) 803, 804 are connected to receive and buffer thesensor data from the two Hall devices. The buffered sensor data is thenprovided to analog to digital converters (ADC) 805, 806 to produce asample digital stream that represents the strength of the orthogonalmagnetic field components.

Angle and speed calculation logic 807 may then process the digitalstreams to calculate the instantaneous angular position and theinstantaneous rotational velocity based on the change of angularposition using known or later developed algorithms. For example, theangle may be determined based on the two field strength signals byeither calculating a four quadrant arc tangent directly or using anon-linear observer to compute the angle indirectly, as described inmore detail above.

Motor controller and drive logic 808 may then generate phase signals 809a-809 c for the field windings in stator 810. Known or later developedtechniques may be used to produce the phase signals. For example, thewell known Clarke and Park transforms may be used. Through the use ofthe Clarke transform, the direct (Id) and quadrature (Iq) currents canbe identified. The Park transform can be used to realize thetransformation of the Id and the Iq currents from the stationaryreference frame to the moving reference frame and control the spatialrelationship between the stator vector current and rotor flux vector.The operation of Park and Clarke transforms are described in more detailin “Clarke & Park Transforms on the TMS320C2xx”, Texas Instruments,BPRA048, 1997, which is incorporated by reference herein.

In some embodiments, linear Hall devices 801, 802 may be packaged inseparate packages. AFE 803, 804, ADC 805, 806, angle logic 807 andcontrol logic 808 may all be provided in a single integrated circuit,such as a C2000™ Piccolo™ F2805x microcontroller device available fromTexas Instruments.

In another embodiment, linear Hall devices 801, 802, AFE 803, 804, ADC805, 806, angle logic 807 and control logic 808 may all be provided in asingle integrated circuit such that an entire FOC motor control anddrive system is provided in a single integrated circuit.

FIG. 9 is an illustration of placement of two linear Hall sensors 901,902 in a 2D array in an exemplary PMSM 900. Motor housing 911 surroundsa stator that includes field windings 912. A rotor 920 is configured torotate within housing 911. An end cap 914 is configured to mate withmotor housing 911. End cap 914 includes a bearing support to mate withrotor bearing 913.

A printed circuit board 940 is mounted on end cap 914. Motor controller901 is mounted on substrate 940 and includes buffers, ADCs, angle/speedlogic, and control/drive logic described in more detail with regard toFIG. 8. Linear Hall devices 901, 902 are mounted on substrate 940 in aposition that will place them close to rotor 920 during normal operationof PMSM 900. Linear Hall device 901 may be positioned to be sensitive toradial magnetic flux produced by the rotor magnets of rotor 920, whilelinear Hall device 902 may be positioned perpendicular to Hall device901 in order to be sensitive to tangential magnetic flux produced byrotor magnets of rotor 920.

In another embodiment, linear Hall devices 901 and 902 may be fabricatedwithin a same integrated circuit that includes all of the control anddrive logic 901 required to control PMSM 900. In this manner, a singleintegrated microcontroller may be used to sense magnetic flux producedby the rotor magnets of rotor 920 in order to accurately determine rotorspeed and position and to generate the phase signals provided to fieldwindings 912 of PMSM 900.

In a another embodiment, instead of measuring the radial and tangentialfields, a pair of perpendicularly arranged Hall sensors may be used tomeasure the axial and tangential end fields at the end of the rotor.From an assembly point of view, this configuration may be moreconvenient. If a surface mount package containing both Hall sensors isused, a horizontal and vertical sensor would be required as before.

FIG. 10 is a schematic illustrating an electrical equivalent of a Halldevice, such as horizontal Hall device 200 or vertical Hall device 500.In this model, assume the bias current is injected at port N and removedat port S, and the Hall voltage is measured across ports W and E. Thereis an effective channel resistance R1 to the bias current and a channelresistance R0 in the Hall voltage path. There is also a Wheatstonebridge resistance effect represented by resistors R2-R5. There istypically a large offset due to resistor mismatch in the Wheatstonebridge type electrical model that is unavoidable even with thestate-of-the-art lithography and fabrication processes. Each and all ofthese resistance effects may vary over time and temperature tocontribute to the offset voltage drift.

A bias current compensation technique referred to as “spinning current”may be used to at least partially reduce the offset. In this technique,the bias current is provided sequentially to at least two differentpairs of contacts N, S, E, W on the Hall element. Superposition of thesupplied currents results in a continuously spinning current vector inthe Hall device. By simultaneously measuring the voltages betweencorresponding terminals, a signal containing the Hall voltage and aperiodic offset voltage can be isolated. The offset voltage may beeliminated by averaging the signal over at least one period.

FIG. 11 is a flow diagram illustrating operation of a linear Hall devicebased field oriented control motor drive system. Referring back to FIG.1, the rotor magnets of a PMSM, such as PMSM 100, may produce a magneticfield that has radial, axial, and tangential components, depending onthe sampling point of reference. During operation of PMSM 100, at leasttwo signals indicative of orthogonal magnet field components produced bythe rotor of PMSM 100 are generated 1102 using two or more perpendicularlinear Hall devices. For example, a first linear Hall device may producea first signal indicative of a strength of a first magnetic fieldcomponent produced by the rotor magnets included within a rotor of theelectric motor 100 while a second linear Hall device may simultaneouslyproduce a second signal indicative of a strength of second magneticfield component produced by the rotor magnets that is approximatelyorthogonal to the first magnetic field component. One of the magneticfield components may be a radial component, while the second magneticcomponent may be a tangential or an axial component, for example.

An angular position and angular velocity of the rotor may be calculated1104 based on the signals from the linear Hall devices using known orlater developed algorithms.

A plurality of phase signals may then be produced 1106 based on thecalculated angular position and angular velocity using known or laterdeveloped algorithms.

The current in a plurality of field windings of the motor may then becontrolled 1108 using the plurality of phase signals using known orlater developed algorithms. For example, Clarke and Park transforms maybe used to produce a set of pulse width modulated signals that may becombined to form phase signals for the field windings that aresinusoidal, trapezoidal, etc.

In this manner, an accurate and low cost field oriented control motordrive system may be provided in a single integrated circuit package thatdoes not require any additional sensor devices or auxiliary sensingmagnets.

Other Embodiments

While the invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various other embodiments of the invention will beapparent to persons skilled in the art upon reference to thisdescription. For example, while a cross shaped device is illustratedherein, other element shapes may be patterned, such as an octagon orsubstantially octagonal, a triangle or substantially triangular, aquatrefoil or substantially quatrefoil shaped, a circle or substantiallycircular shape, etc. Similarly, depending on the geometry of Hallelement layer, the number of contact pads and corresponding wires may bealtered to fit a given application.

In some embodiments, the linear Hall devices may be packaged in separatepackages. In some embodiments, the linear Hall devices and all of thebuffering and processing logic may be packaged in a single integratedcircuit.

While a two dimensional array of two perpendicular Hall devices wasdescribed herein, other embodiments may include more than two Halldevices. For example, three Hall devices may be used to sensetangential, radial, and axial magnetic flux components.

While an exemplary PMSM was described herein, other embodiments of thedisclosure may be use to control other motor configurations, such as onein which the rotor surrounds the field windings. Other embodiments maybe used to control “pancake” style motors, etc.

The techniques described in this disclosure may be implemented inhardware, software, firmware, or any combination thereof. For example,the angular position and speed determination process may be performed insoftware. Similarly, the motor control processing may be performed insoftware. If implemented in software, the software may be executed inone or more processors, such as a microprocessor, application specificintegrated circuit (ASIC), field programmable gate array (FPGA), ordigital signal processor (DSP). The software that executes thetechniques may be initially stored in a computer-readable medium such ascompact disc (CD), a diskette, a tape, a file, memory, or any othercomputer readable storage device and loaded and executed in theprocessor. In some cases, the software may also be sold in a computerprogram product, which includes the computer-readable medium andpackaging materials for the computer-readable medium. In some cases, thesoftware instructions may be distributed via removable computer readablemedia (e.g., floppy disk, optical disk, flash memory, USB key), via atransmission path from computer readable media on another digitalsystem, etc.

Certain terms are used throughout the description and the claims torefer to particular system components. As one skilled in the art willappreciate, components in digital systems may be referred to bydifferent names and/or may be combined in ways not shown herein withoutdeparting from the described functionality. This document does notintend to distinguish between components that differ in name but notfunction. In the following discussion and in the claims, the terms“including” and “comprising” are used in an open-ended fashion, and thusshould be interpreted to mean “including, but not limited to . . . ”Also, the term “couple” and derivatives thereof are intended to mean anindirect, direct, optical, and/or wireless electrical connection. Thus,if a first device couples to a second device, that connection may bethrough a direct electrical connection, through an indirect electricalconnection via other devices and connections, through an opticalelectrical connection, and/or through a wireless electrical connection.

Although method steps may be presented and described herein in asequential fashion, one or more of the steps shown and described may beomitted, repeated, performed concurrently, and/or performed in adifferent order than the order shown in the figures and/or describedherein. Accordingly, embodiments of the invention should not beconsidered limited to the specific ordering of steps shown in thefigures and/or described herein.

It is therefore contemplated that the appended claims will cover anysuch modifications of the embodiments as fall within the true scope andspirit of the invention.

What is claimed is:
 1. A method for controlling an electric motor, themethod comprising: producing a first signal indicative of a strength ofa first magnetic field component produced by a set of rotor magnetsincluded within a rotor of the electric motor using a first linear Halldevice; simultaneously producing a second signal indicative of astrength of second magnetic field component produced by the rotormagnets that is approximately orthogonal to the first magnetic fieldcomponent using a second linear Hall device; calculating an angularposition and angular velocity of the rotor based on the first signal andthe second signal; producing a plurality of phase signals based on thecalculated angular position and angular velocity; and controllingcurrent in a plurality of field windings of the motor using theplurality of phase signals.
 2. The method of claim 1, in which the firstlinear Hall device is located adjacent the rotor, and in which thesecond linear Hall device positioned perpendicular to the first linearHall device.
 3. A motor drive system comprising: a multidimensionalarray of at least a first linear Hall device and a second linear Halldevice; angle-speed calculation logic coupled to receive signalsindicative of magnetic field strength from each of the linear Halldevices; and motor controller and drive logic coupled to receive angularspeed information from the angle-speed calculation logic, with aplurality of outputs for providing a plurality of phase signals tocontrol a motor.
 4. The system of claim 3, in which the second linearHall device is positioned perpendicular to the first linear Hall device.5. The system of claim 3 in which the multidimensional array of Halldevices, the angle-speed calculation logic and the motor controller anddrive logic are all formed on a single integrated circuit, (IC).
 6. Apermanent magnet synchronous motor (PMSM) comprising: stator having aplurality of field windings, in which the plurality of phase signals arecoupled to the field windings; rotor configured to rotate with referenceto the stator, the rotor having a plurality of rotor magnets; a motordrive system positioned so as to be within a magnetic field produced bythe rotor magnets, in which the motor drive system includes a firstlinear Hall device and a second linear Hall device positionedperpendicular to each other.
 7. The PMSM of claim 6, in which the motordrive system further includes: angle-speed calculation logic coupled toreceive signals indicative of magnetic field strength from each of thelinear Hall devices; and motor controller and drive logic coupled toreceive angular speed information from the angle-speed calculationlogic, with a plurality of outputs for providing a plurality of phasecoupled to the field windings of the stator.
 8. The PMSM of claim 7, inwhich the first linear Hall device, the second linear Hall device, theangle-speed calculation logic and the motor controller and drive logicare all formed on a single integrated circuit (IC).